Effects of Aging on Rheumatoid Factor and Anticyclic Citrullinated Peptide Antibody Positivity in Patients With Rheumatoid Arthritis

OBJECTIVE: We investigated the factors that affect rheumatoid factor (RF) and anticyclic citrullinated peptide antibody (anti-CCP) positivity in patients with rheumatoid arthritis (RA). METHODS: The study included all consecutive patients with RA treated at Keio University Hospital between 2016 and 2017. We recorded age at diagnosis, sex, smoking habit, BMI (kg/m2), and family history, and investigated the association between these variables and RF and anti-CCP positivity. RESULTS: We recruited 1685 patients with RA. The mean age at diagnosis was 51.9 years, and 83.4% of the patients were women. Positivity rates of RF and anti-CCP almost linearly decreased along with the increase in age at RA diagnosis (grouped by decade) after ≥ 30 years of age (RF: 80.5%, 84.2%, 81.1%, 78%, 74.6%, 62.6%, 51.4%, P < 0.001; anti-CCP: 79.9%, 87.4%, 81.7%, 74%, 70.5%, 60.2%, 37.1%; P < 0.001). Multivariable analysis revealed that age was independently associated with seronegativity in women (RF: odds ratio [OR] 0.98, 95% CI 0.97-0.99, P < 0.001; anti-CCP: OR 0.97, 95% CI 0.96-0.98; P < 0.001), nonsmoking history (RF: OR 0.98, 95% CI 0.97-0.99, P < 0.001; anti-CCP: OR 0.97, 95% CI 0.96-0.98; P < 0.001), and BMI < 25 (RF: OR 0.98, 95% CI 0.97-0.99; P < 0.001; anti-CCP: OR 0.97, 95% CI 0.97-0.98; P < 0.001). CONCLUSION: Aging is an independent contributor for seronegative RA in patients who are female, have a nonsmoking history, and a BMI < 25.